package com.jiabo.sqlSession;

import com.jiabo.pojo.Configuration;
import com.jiabo.pojo.MappedStatement;

import java.lang.reflect.*;
import java.util.List;

public class DefaultSqlSession implements SqlSession {

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... params) throws Exception {
        //将完成对simpleExcuter里面的query方法的调用
        simpleExecutor simpleExecutor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappdeStatementMap().get(statementId);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);
        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementId, Object... params) throws Exception {
        List<Object> objects = selectList(statementId, params);
        if (objects.size() == 1) {
            return (T) objects.get(0);
        } else {
            throw new RuntimeException("查询结果为空，或者返回结果过多");
        }
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        //使用jdk动态代理来为Dao生成代理对象并返回
        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                //根据不同情况来调用selectList或者selectOne
                //准备参数：1.statementId：sql语句唯一标识namespace.id = 接口全限定名+方法名
                //方法名：findAll
                String methodName = method.getName();
                //接口全限定名
                String className = method.getDeclaringClass().getName();
                String statementId = className + "." + methodName;
                //准备参数2 入参：args
                //获取被调用方法的返回值类型
                Type genericReturnType = method.getGenericReturnType();
                if (genericReturnType instanceof ParameterizedType) {
                    //判断是否进行了泛型类型参数化（有泛型就是一个集合）
                    return  selectList(statementId, args);
                }
                return selectOne(statementId, args);
            }
        });
        return (T) proxyInstance;
    }
}
